Inlet air cooling device and method for internal-combustion engines



March 8, 1955 K. FROEHLICH 2,703,561

INLET AIR COOLING DEVICE AND METHOD FOR INTERNAL-COMBUSTION ENGINES Filed Jan. 13, 1954 United States Patent Kurt Froehlich, Milwaukee, Wis., assignor to Nordberg Manufacturing Company, Milwaukee, Wis., a corporation of Wisconsin Application January 13, 1954, Serial No. 403,864

8 Claims. (Cl. 123-119) My invention is in the field of internal combustion engines and more specifically is a mechanism and method for increasing the horsepower output and the mean effective pressure of an engine without increasing its thermal load.

More specifically my invention relates to or is in the nature of an attachment for a two-cycle engine. It essentially is a means and method for decreasing the temperature of the supercharged inlet air so as to reduce the final compression temperature in the cylinders prior to ignition and burning of the fuel.

A primary object of my invention is a mechanism and method of the above type for increasing the load carrying capacities of an engine.

Another object of my invention is a device or mechanism in the nature of an attachment for use with an internal combustion engine of the two-stroke cycle type which is constructed to be quickly and easily applied to a known engine to increase the load capacity that the engine will carry.

Another object of my invention is an attachment of the above type specifically constructed and arranged for use with a two-stroke cycle engine.

Other objects will appear from time to time in the I ensuing specification and drawings in which I have diagrammatically illustrated a schematic representation of my invention.

In the drawings an engine is generally indicated at E and has the usual inlet and exhaust manifolds 2 and 4 respectively. The drive shaft 6 ofthe engine is coupled to a volumetric blower 8 through a suitable coupling 10.

The blower 8 draws in inlet air through an intake duct 11 and compresses it substantially so as to increase its density and pressure. A continuous flow of air is conveyed from the blower through a suitable connection 12 to an attachment indicated generally at A, which includes a centrifugal compressor 14 which receives the air through the connection 12 and further compresses it. The hot highly compressed air is taken from the compressor 14 by a pipe or conduit 16 to an intercooler 18 which reduces its temperature. The pressure of the air is held approximately constant as it passes through the intercooler and due to the withdrawal of heat from the air and a substantial reduction in its temperature, its

density is substantially increased. Any suitable cooling fluid may be used in the intercooler.

From the intercooler 18, the air is conveyed to an expander 20 by a suitable connection 22. The expander can be a conventional device for expanding and reducing the pressure of the air and at the same time causing a substantial drop in its temperature. The air is conveyed from the expander by a suitable conduit 24 to the intake manifold of the engine, where the normal engine cycle of compression, ignition and expansion follows. The expander is directly connected or coupled to the com- PICZSZOI 14 by a suitable connection indicated generally at The above described system and mechanism will operate satisfactorily on a two-stroke cycle engine and will substantially increase itsload carrying capacities at full load conditions; however, at partial loads below full load, the engine will be supplied with too much air, because the blower 8 is, as stated above, the volumetric type and delivers a constant quantity of air regardless of the load on the engine. It will be understood that the engine is operated by a suitable governor which controls and regulates the engine at a constant speed for varying loads. Thus, regardless of the load on the engine, the drive shaft 6 will be at an approximately constant speed and the quantity of air delivered from the blower 8 and the pressure rise across it will be approximately constant for all loads. It is therefore necessary at partial loads to control the output from the blower. In essence, this inyolves reducing the quantity of air that is delivered to the compressor 14 without varying the pressure.

In the drawings I have shown a control mechanism, indicated generally at C. A thermally responsive control element 28 is positioned in the path of the exhaust gas in the exhaust manifold. This element is temperature sensitive and is in communication with a controller 30 through a tube 32. High pressure air or any other suitable fluid from a suitable source, not shown in the drawings, is supplied to the controller by a connection 34. The fluid is conveyed by a connection 36 to a bellows or diaphragm element 38, the controller serving to meter -or control both the pressure and quantity of the air passing through it. The diaphragm element is a chamber with a flexible diaphragm 40 separating its two halves.-

The upper half of the chamber is in communication with the source of high pressure air while the lower half has an operating rod 42 which is biased upwardly by a coil spring 44. This device in essence is a motor type element imparting movement to the rod 42. The spring 44 biases the rod upwardly, as shown in the drawings, in opposition to the downward movements imparted to it by the pressure of the air applied to the diaphragm 40 from the source through the controller. The rod 42 is connected through a suitable linkage 46 to a butterfly valve 48 positioned in a bypass passage 50. This passage is connected to the inlet and exhaust sides of the volumetric blower 8 and establishes communication between them. A butterfly valve 48 controls this passage, and regulates the quantity of air passing through it in response to movements of the diaphragm 40.

The use, operation, and function of my invention are as follows:

The energy derived from expansion of the air in the expander is returned and used in the compressor bythe connection 26. Expanders of the type in use at the present time have an efliciency within definitely defined limits. This is also true of centrifugal compressors. Consequently, to drive the compressor from the expander alone, a much larger pressure drop across the expander must take place than the pressure rise across the compressor 14. It will be understood that if the combination of the compressor 14 and the expander 20 was per cent eflicient, the temperature drop across the expander would exactly equal the temperature rise in the compressor, and the amount of energy derived from expansion would be returned by the shaft or connection 26 and would be exactly the amount required to drive the compressor 14.

The added increase in the energy in the air in the system is supplied by the volumetric blower 8. Thus, the combination of the two energy rises, one in the volumetric blower 8 and the other in the compressor 14, provides sufficient energy in the air at the inlet to the expander 20 so that a sufncient temperature drop may take place across the expander without the outlet pressure from the expander being below atmospheric pressure.

It is important in a two-cycle engine that the inlet scavenging pressure be above atmospheric pressure when the engine is exhausting to the atmosphere, so that the cylinders will be properly scavenged between the expansion and compression strokes.

I have shown the blower 8 as being directly coupled to the engine in a direct drive. In certain installations, for example marine and locomotive, it is extremely desirable that the engine be reversed on occa ion. It would therefore be necessary to provide an appa atus whereby the blower could be disconnected from the drive shaft and driven by another source while the engine is reversed. Theincrease in the frictional losses in such a system as I propose would be small and, therefore, adequately counterbalanced by the gain in horsepower output. In addition, my invention will reduce the specific fuel consumption of the engine.

By using an attachment of this nature, theoretically the compression ratio and ex creased without reaching the etonatton point in a given octane fuel.

The control mechanism C operates as follows: The temperature of the exhaust gases is an indication of the load on the engine when a constant amount of air is being supplied. For example, if the load on the engine decreases, the governor automatically supplies less fuel to the engine while maintaining its speed approximately constant. With the fuel quantity decreased, the engine will be operating with an excess of air and the exhaust gases will tend to be cooler. If the load on the engine increases and the governor supplies a larger quantity of fuel, the mixture in the cylinders will be richer and the temperature of combustion will be higher, and the exhaust temperature will increase.

The temperature sensitive element 28 responds to the temperature variations in the exhaust gases and signals the controller 30. The controller responds to the signals, so to speak, from the element 28 and varies the pressure of the air being supplied from the high pressure source to the diaphragm mechanism C. As the temperature of the exhaust increases indicating a higher load, the controller lowers the pressure of the air conveyed to the diaphragm mechanism C. The spring 44 forces the link 42 and its connection 46 upward as shown in the drawing and closes the butterfly valve 48. Thus, the quantity of air being supplied by the blower 8 to the compressor 14 will be increased. At full load, the butterfly valve 48 will be completely closed, the bypass 50 will be blocked, and the maximum quantity of air will be supplied to the attachment A by the blower 8. 7

When the load decreases, the temperature of the exhaust gases will also decrease, because excess air is being supplied to the engine. The element 28 causes the controller 30 to increase the pressure of the air on the diaphragm 40, and the linkage is lowered, opening the butterfly valve 48. Thus, a portion of the air supplied by the blower will re-cycle through the bypass 50.

I have stated previously that the invention is considered to be in the nature of an attachment for a twocycle engine. This is important because two-cycle engines are customarily provided with volumetric scavenging blowers, as indicated at 8, to scavenge them properly. Thus my invention can take the form of an attachment including the compressor, intercooler and expander with the bypass 50 and its control mechanism.

It should be understood that the engine used with the invention could be either a diesel, a gas engine, or a sparkignition engine.

Whereas, I have shown and described a preferred form of my invention, various modifications, alterations and changes can be made without departing from its functional theme, and I desire that the invention be unrestricted except as by the appended claims.

I claim:

1. In a device for cooling the inlet air for an internal combustion engine including means for initially compressing the inlet air, means for er compressing the inlet air, means for cooling the air after it has been comansion ratio could be inpressed, and means for expanding the air from the cooling means and supplying it to the engine, the expanding means being associated with one of the compressing means to drive it, the other compressing means being driven by the engine.

2. In a device for cooling the inlet air for an internal combustion engine, including a centrifugal compressor and an engine-driven volumetric compressor in series with each other for compressing the inlet air, an intercooler for cooling the air after it has been compressed, and an expander for reducing the temperature and pressure of the air and supplying it to the engine, the exgander being coupled to the centrifugal compressor to rive it. I

3. The structure of claim 2 wherein the engine driven volumetric compressor draws in atmospheric air and initially compresses it and the centrifugal compressor receives the air from the volumetric compressor and further compresses it.

4. In a device for cooling the inlet air for a two'stroke cycle internal combustion engine having an en e-driven volumetric compressor, compressing means or compressing the inlet air after it has been initially compressed by the engine-driven volumetric compressor, means for cooling the inlet air from the compressing means, and means for expanding the air from the cooling means and supplying 'it to the intake manifold of the engine, the compressing means being driven by the expanding means.

5. In a device for cooling the inlet air for a two-stroke cycle internal combustion engine having an engine-driven volumetric compressor, including compressing means adapted to be connected in series with the engine/driven volumetric compressor, means for cooling the air after it has been compressed by both the compressing means and the engine-driven volumetric compressor, and means for expanding the air after it has geen cooled and sup plying it to the intake manifold of the engine, the compressing means being driven by the expanding means.

The structure of claim 5 wherein the air is supplied from the engine-driven volumetric compressor to the compressing means. v

7. A method of cooling the inlet air for an internal combustion engine comprising the steps of initially compressing the inlet air, further compressing the inlet air, cooling the air after it has been compressed, expanding the air to a reduced temperature after it has been cooled, using the'energy derived from the expanding step to perform one of the compressing steps, and using energy from the engine for performing the other compressing steps.

8. A method of cooling the inlet air for a two-stroke" cycle internal combustion engine having an enginedriven volumetric compressor comprising the steps of compressmg the inlet air in addition to the compression etIectecl in the volumetric compressor, cooling the air after it has been compressed, expanding the air after cooling it to a reduced temperature, and using the energy of expansion to perform the previous step of fompressing the air.

No references cited. 

